Slightly OT - looking for power adapter info for Palm III GPS

The Palm isn't quite 10 years old yet, but at least this is cool hand-held tech... I have this Rand McNally Navman/Streetfinder GPS that wraps around a Palm III, and I have lost track of which wall wart charges it up. There is, of course, no power information molded into the case, and as of yet, I have been unable to google any specs. Does anyone on the list happen to have one of these, or even just know what the input voltage is? I suspect it might be 12V, so that a simple lead can charge it in the car, but even an examination of the innards hasn't been revealing. I did run across a variable voltage car adapter with the right tip set to 9V. Since I don't have many devices with that particular tip (it's the smallest female coax connector in the standard Radio Shack kit), I have reason to suspect that I may have rigged this up some years ago, but I have no direct proof. I realize I should have scrawled the power info on the back with a Sharpie, something I will now do, once I put this thing back in service. Thanks for any tips, -ethan